EXCEL 10 W7761A INPUT/OUTPUT DEVICE
18
74-2699
It is important to understand these interrelationships early in the job engineering process to ensure implementing when
configuring the controllers. (See Application Step 6. Configure Devices, for information on the various Excel 10 parameters and
on Excel 10 point mapping.)
Step 2. Determine Other Bus Devices Required
A maximum of 62 nodes can communicate on a single E-Bus segment. Each W7761A (RIO), W7750 (CVAHU), W7751 (VAV)
Controller or T7780 Wall Module constitutes one node. If more nodes are required, a Q7751A Router is necessary. Using a
router allows up to 125 nodes, divided between two E-Bus segments. The router accounts for two of these nodes (one node on
each side of the router); a Q7750A Excel 10 Zone Manager takes one node and two nodes are available for operator terminal
nodes, leaving 120 nodes available for Excel 10 Controllers and T7780 Wall Modules. All 120 controllers and T7780 Wall
Modules are able to talk to each other through the router. A Q7750A Excel 10 Zone Manager is required to connect the E-Bus
to the standard EXCEL 5000® System C-Bus. Each Excel 10 Zone Manager can support no more than 120 Excel 10
Controllers and T7780 Wall Modules. This limit is set in the Excel 10 Zone Manager database as an absolute maximum.
Each E-Bus segment is set up with two unused nodes to allow for a CARE/E-Vision or Hand Held Tool (HHT) to be connected
to the E-Bus. Multiple CARE/E-Vision or HHT terminals can be connected to the bus at the same time. Table 4 summarizes the
E-Bus segment configuration rules.
Table 4 . E-Bus Configuration Rules And Device Node Numbers.
One E-Bus Segment Example
Maximum Number of Nodes Equals 62
One Q7750A Excel 10 Zone Manager 1 node
Port for operator terminal access (CARE/E-Vision or HHT) 1 node
Maximum number of Excel 10s and T7780s 60 nodes (Only T7780 Wall Modules are E-Bus nodes)
Total 62 nodes
Two E-Bus Segments Example Maximum Number of Nodes Equals 125
One Q7750A Excel 10 Zone Manager 1 node
One Q7751A Router 2 nodes (1 in each Bus Segment)
Ports for operator terminal access (two CARE/E-Vision or HHT
terminals)
2 nodes (1 in each Bus Segment)
Maximum number of Excel 10s and T7780s in segment number
one
60 nodes (Only T7780 Wall Modules are E-Bus nodes)
Maximum number of Excel 10s and T7780s in segment number
two
60 nodes (Only T7780 Wall Modules are E-Bus nodes)
Total 125 nodes
Refer to the E-Bus Wiring Guidelines form, 74-2865 for complete description of network topology rules and the maximum wire
length limitations. If longer runs are required, a Q7740A 2-way or Q7740B 4-way repeater can be added to extend the length of
the E-Bus. A Q7751A Router can be added to partition the system into two segments and effectively double the length of the
E-Bus. Only one router is allowed with each Excel 10 Zone Manager and each network segment can have a maximum of 1
repeater. In addition, all E-Bus segments require the installation of a Bus Termination Module for a singly terminated E-Bus or
two Bus Termination Modules for a doubly terminated E-Bus. For more details on E-Bus termination, refer to the E-Bus Wiring
Guidelines form, 74-2865, or see Application Step 3. Lay Out Communications and Power Wiring, and the E-Bus Termination
Module subsection in Application Step 4.
Step 3. Lay Out Communications and Power Wiring
E-Bus Layout
The communications bus, E-Bus, is a 78-kilobit serial link that uses transformer isolation and differential Manchester encoding.
Approved cable types for E-Bus communications wiring is Level IV 22 AWG (0.34 mm
2
) plenum or non-plenum rated
unshielded, twisted pair, solid conductor wire. For nonplenum areas, use Level IV 22 AWG (0.34 mm
2
), such as U.S. part
AK3781 (one pair) or U.S. part AK3782 (two pair). In plenum areas, use plenum-rated Level IV, 22 AWG (0.34 mm
2
) such as
U.S. part AK3791 (one pair) or U.S. part AK3792 (two pair). See Tables 9 and 10 for part numbers. Contact Echelon
Corp.
Technical Support for the recommended vendors of Echelon
approved cables. The FTT communications bus, E-Bus,
supports a polarity insensitive, free topology wiring scheme that supports star, loop, and/or bus wiring.
E-Bus networks can be configured in a variety of ways, so refer to the E-Bus Wiring Guidelines form, 74-2865 for a complete
description of network topology rules and Table 4. Fig. 9 and 10 depict two typical E-Bus network topologies; one as a singly
terminated bus segment that has 60 nodes or less, and one showing a doubly terminated segment. The bus configuration is
set up using the Network Manager tool from within CARE (see the CARE User’s Manual form, 74-5587 or Excel E-Vision
User’s Guide form, 74-2588).
